Connector pins have many uses including use on a tractor draw bar for connecting the tongue of a pulled wagon or the like to the draw bar. A common problem in the draw bar use is that the pin becomes disengaged from the draw bar by bouncing out or hitting rough terrain under the draw bar. A serious safety problem is created when this happens, as the towed vehicle will be released and will move out of control. It is thus seen that it is very important to have a lock means on the draw bar pin which is fool proof in operation, but is easy to put on and take off.